The striker's representative has brought the club down to earth with a bang after claiming the player will definitely be leaving in the summer
The likes of Bayern Munich, Juventus, Manchester United and Manchester City are all believed to be keen on luring the Poland international away from Signal Iduna Park this summer.
BVB have so far stressed that they have no intention of selling their star attacker, though a transfer now seems inevitable following comments made by the player's representative on the the back of one of the finest nights in the club's history.
"We have reached an agreement with another club and intend to switch clubs this summer," Barthel was quoted as saying by Sport Bild.
"All of Borussia Dortmund's demands will be met."
Lewandowski's agent then went on to stress that BVB have promised the striker that he will be allowed to leave under the right conditions and expects Jurgen Klopp's side to honour their promise.
"There is an interesting offer for Robert that meets Dortmund's criteria and satisfies Robert's demands. BVB have assured us that Robert will be allowed to leave under these circumstances. It's now up to the clubs to sort it out."
Despite Barthel's claims, Dortmund general manager Hans-Joachim Watzke has denied that their star striker is set to leave Signal Iduna Park in the summer and says that dialogue with resume with forward soon.
"No, it is not true [that Lewandowski has agreed to move elsewhere]. We don't have any offer of another club," he told German news agency SID. "We will talk about everything with Robert."
The 24-year-old has a contract until the summer of 2014, with his exit another potential hammer blow for Dortmund following the news Mario Gotze will join rivals Bayern Munich in the summer.